Nitrates are a proven performance enhancer, increasing
muscle efficiency with a decrease in the amount of oxygen used for
any level of exercise. And this occurs without an increase in blood lactate
levels (which, if elevated might suggest alternative energy pathways were being
stimulated). This increased efficiency has been demonstrated with diet changes alone
(100-300 g of a nitrate-rich vegetable such as spinach or beetroot for 2 days) for both
sub-maximal levels of exertion
as well as for maximal levels of exertion.
The same degree of improvement has been documented with pure nitrate as a
pharmaceutical grade supplement as well.

The duration of improvement
in exercise performance is between 5 and 30 minutes. Specific studies:

In the first study, 6 days of
supplementation produced a slight improvement in 10k time trial performance (953 vs. 965 seconds)
with a slightly higher average power output of 294 vs. 288 watts
with a lower overall rate of oxygen consumption.

In the second, assessing the benefits
of acute use, nine club-level competitive male cyclists were given a single dose
of 0.5 L of beetroot juice (containing 6.2 mmol of nitrate) 2 1/2 hours before a 4 and 16 km time trial.
The 4-km performance improved by 2.8% and the 16.1-km performance by 2.7%.

But as expected with a duration of effect in the range of 30 minutes, there was
no clear benefit in a
longer duration 50 mile time trial.

How do nitrates work? One theory is an improvement in muscle response to nerve stimulation, perhaps by
allowing for more muscle cell "recruitment" for any level of nerve impulse
stimulation. For example, if a nerve impulse normally would stimulates 80%
of the cells in a muscle, the nitrates might increase that to 82%. So
as your brain signals for muscle activity, it gets a small bonus.

It is not the nitrate molecule itself that provides this performance benefit, but a
metabolic end product, nitric oxide. Nitrate is an inorganic anion which is particularly
abundant in green leafy vegetables such as spinach, beetroot, rocket, or lettuce.
It is converted into nitrite [NO2-] by bacteria in the mouth. The nitrite is
absorbed into the systemic circulation and subsequently reduced to the active
agent nitric oxide (NO). Nitric oxide is known to be an important "signaling molecule" at
the cell level is assumed to be
the active agent
improving the nerve/muscle interaction. And it appears that this benefit is
directly related to the ability of the diet or supplement to elevate the
plasma [NO2-].

Before we address the question as to who might benefit from nitrate supplements, it is
important to note that nitrates are not on the World Anti-Doping Agency's
(WADA) Prohibited List.
A recent review
concluded that both acute and more chronic dietary nitrate
supplementation improved cycle efficiency (and thus time trial performance) for events
of 5 to 30 min duration in trained, but sub-elite, cyclists. But the same
studies have not found an effect in the highly trained endurance athletes. The studies
showing negligible benefits of nitrates in these elite athletes
used acute (2 to 3 hours before the ride) and short-term (3 day before the ride) supplementation
protocols which leaves open the possibility that longer-term supplementation,
and/or higher nitrate doses, might improve performance in this group of elite athletes.
Here is a bit more detail for those interested in teasing out
the relationship between level of training versus the benefit of oral nitrates. To
quote: "In conclusion, our study shows that the ergogenic effects of nitrate supplementation are
significantly related to the individual aerobic fitness level, with no benefits observed on highly
trained subjects (VO2peak > 60 mL/kg/min). These different effects on O2 cost of exercise and
performance seem related to the relative changes in plasma [NO3-] and [NO2-]... provides further
evidence to the notion that nitrate supplementation might be ergogenic if it results in an
appreciable increase of plasma [NO2-]. The optimal nitrate-loading regimen required to
elevate plasma [NO2-] and to enhance performance in elite athletes is different from that
of low-fit subjects and requires further attention.

Bottom line - for all except the very top elite cyclists, both short term (single pre event dosing) as well
as longer term (7 day) supplementation look provide equal performance enhancement.

How much nitrate is necessary to provide a performance benefit? For single dose, acute supplementation, most
studies used 6 to 8 mmol of nitrate taken 2 hours before the activity.
One paper
looked at larger doses and found no benefit above 8.4 mmole nitrate. For chronic, multi day
supplementation, the same dosages were used, only for longer periods of time.

Where do you get
dietary nitrates (besides beets)? Celery, cress, chervil, lettuce,
red beetroot, spinach, rocket (rucola) are all
high in nitrate with > 250 mg nitrate per 100 gm of vegetable. But the preparation
of the vegetable, beets for example, makes a difference. Home processed beets
were found to be significantly higher in nitrate content than the commercially
processed beets. This difference was attributed to differences in processing methods.
Pickled and Harvard beets contained significantly lower amounts of nitrate/nitrite
on a dry weight basis than the other types of processed beets.

How does 8.4 mmole of nitrate convert into beets (assuming 250 mg nitrate per
100 gram of vegetable as mentioned above).?

As an alternative to beets, several studies used 500 ml (~17 ounces) of beet
juice as a single dose or daily.

Finally there are various supplements on the market that might be considered.
But if you are going to use a supplement, check on the nitrate content. It is not
always indicated on the label. I had to send 2 emails
to Beetelite to find that it had
only 250 mg of nitrate per dose.

Beet (or other nitrate) supplement should be taken at least 2 to 2.5 hours before the event (if a single
acute supplement is being used) or for 2 to 6 days if a chronic dietary change is planned.

Is this emphasis on nitrates worth it? To quote:
"It should be emphasized that 5 to 9Êmmol of nitrate can readily be consumed within
the normal diet and there is presently no evidence that additional nitrate intake
produces greater benefits." So for the average cyclist, who is eating a balanced diet,
supplements may be more than is needed. And if in doubt, eat an extra serving of greens and
occasional beets. There is little to be lost, and for the elite athlete a definite potential for gain
from a trial of beet juice as a supplement or a change to a high nitrate diet (spinach, beet root, rocket).
For those interested in more information, this is a
nice summary article.

How about safety? In 2015 there was a
WHO report indicating
a significant cancer risk with processed meats, and implicated nitrates as the culprit. How about
nitrates in vegetables (beets, celery, spinach, etc.)? There have been several large meta-analyses
(A, B) indicating a protective effect of
vegetarian diets as far as cancer risk was concerned, and one Canadian investigation (referenced in
this study) that specifically called out
nitrate or nitrite and ascorbate-containing foods as having no risk and instead noted they were significantly
protective (from the perspective of an associated cancer risk). The reason?
Most likely due to the associated fiber and other natural organic molecules. I found this to be
a nice but somewhat simplistic overview of
the subject for those looking for more.

Until recently, the production of nitric oxide was thought to occur only via synthesis from
arginine. But beet juice offered another pathway. Now Viagra offers a third pathway to
increase the effects of NO by increasing the sensitivity to NO released from nerve
endings and endothelial cells in the corpus cavernosum of the penis with sexual
stimulation . This NO stimulates an enzyme to convert guanosine triphosphate (GTP) into
cyclic guanosine monophosphate (cGMP). It is then the cGMP that causes the smooth
muscle of the blood vessels in the penis to relax, which in turn causes an inflow
of blood leading to an erection. cGMP is broken down and back to the inactive GMP
by a second enzyme phosphodiesterase type 5 (PDE5). Men who suffer from erectile dysfunction
often produce too little endogenous NO. This means that the small amount of cGMP they
produce is broken down more quickly (the same rate, but less total cGMP to be metabolized)
and therefore doesn't have the time to accumulate and cause the vasodilation effect.
Sildenafil (Viagra) works by inhibiting the enzyme PDE5. This means that cGMP is not
hydrolyzed as fast, accumulates, and this allows the blood vessel smooth muscles to relax.
Sildenafil is a potent and highly selective inhibitor of PDE5. Thus Viagra, by its effect on
metabolic breakdown, increases the effects of a set amount of NO to lead to vasodilation.

The obvious 2 questions are:

Does beet juice lead to more internal NO release and then increase erections? To date,
there have been no controlled studies investigating whether supplementing with beet juice
before sexual activity improves erectile function compared to placebo. But in theory,
it may help a bit and could be worth a try. A natural cure. The caveat is that
without safety data anyone on viagra might get "more bang for the buck" that is an
additional boost from beet juice - I await the first clinical data on the additive
effect of these 2 agents.

Can viagra improve physical performance (ala beet juice) by changing internal NO
degradation? Here the answer is more complex. The
key study
indicated that viagra (alone) does NOT improve performance at sea level
(I await the combo study of viagra and beet juice in combination), but does
help a subgroup of athletes at altitude. And this is where it gets interesting.
If you look at the graph (fig 2) in the original article, the subgroup
benefiting actually responded from the level of a significantly decreased
performance at altitude which was then eliminated (bringing them back to
the level of performance of the non responders).

We know that the production of nitric oxide is elevated in populations living
at high altitudes, which helps these people avoid hypoxia by aiding in pulmonary
vasculature vasodilation. So the findings in this paper suggest that a
sub group (very possibly those prone to the effects of altitude sickness -
headache, pulmonary edema, nausea) are those that will benefit. In this
subgroup, the viagra may reverse metabolic shortcomings that lead to
their sub par performance.

So what are my take aways from my review?

Viagra alone does not appear to help performance at sea level - although
we have prior evidence that beet juice does.

A study on the possible additive benefits of beet juice with viagra
on performance at sea level needs to be done.

If you suffer from the effects of altitude (nausea, headaches), Viagra
may eliminate the metabolic change that are putting you at a disadvantage. And
in this way Viagra may bring you back to a level playing field for a
competitive event.